domain.com #uses the domain to automatically set up SSL with Let's Encrypt
proxy / localhost:8080 #redirect everything to Arc on 8080

I will say that Arc runs a bit resource intensive, and the slightly slow boot times mean you don't want it to have to re-launch because of infrequent requests. I don't know how well it would work on Heroku.

Also, some VPS services like vultr.com offer $5/mo nodes that have more resources than what you get from Heroku at $7/mo anyway.